5428
ISSN 2286-4822
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EUROPEAN ACADEMIC RESEARCH
Vol. V, Issue 10/ January 2018
Impact Factor: 3.4546 (UIF)
DRJI Value: 5.9 (B+)
Quality characteristics of yoghurt made from
various blends of camel’s and cow's milk
ZAKARIA A. SALIH
AZHARI SIDDEEG1
SAHAR G.A. HAMID
Department of Food Engineering and Technology
Faculty of Engineering and Technology, University of Gezira
Wad Medani city, Sudan
AL-FARGA AMMAR
College of Sciences, Biochemistry Department
University of Jeddah, Saudi Arabia
ALI O. ALI
Department of Food Engineering and Technology
Faculty of Engineering and Technology, University of Gezira
Wad Medani city, Sudan
Abstract:
Milk and its products are of high nutritional value and are of
great importance in human nutrition. In Sultanate of Oman, cow’s
milk is normally used in the production of various dairy products.
However, in Salalah and the surrounding area camel milk is more
used than cow’s milk. The aim of this study is to enhance the
utilization of camel milk for the production of yoghurt from blends of
camel and cow’s milk. Three types of yoghurts were made from 100%
cow’s milk and blends of camel and cow’s milk in the proportion of, 15:
85% and 30: 70% of camel's and cow's milk, respectively. Milk as well
as their products were subjected to chemical, microbiological and
sensory evaluation analyses using standard methods. The results
obtained showed very slight difference between the chemical
1 Corresponding author: [email protected]
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
Quality characteristics of yoghurt made from various blends of camel’s and
cow's milk
EUROPEAN ACADEMIC RESEARCH - Vol. V, Issue 10 / January 2018
5429
composition of camel's and cow's milk. The contents of the chemical
components of the last two blends of camels and cow’s milk were
almost identical. On the other hand, the microbial analysis showed
that the camel and cow’s milk were free from Coliform bacteria.
However, it was found that very small numbers of Coliform bacteria
were found in the milk blends at the levels of 0.8 x10 and 0.9×10for the
samples of 30: 70% and 15: 85%. Camels and cow’s milk blends,
respectively. The total bacteria count in the cows and camels milk were
0.3 ×10² and 0.1×10² respectively, while it was 0.5 ×10² and 0.8 ×10² in
the camel's and cow's milk blends of 15: 85 % and 30: 70%
respectively. The results also indicated the presence of very small
numbers of yeasts and molds in all the milk samples. It was found to
be 0.3 × 10, 0.2 × 10 , 0.4 × 10 and 0.1×10² in the camel's and cow`s
blends of 30: 70% and 15:85% respectively. The acidity of the various
types of yoghurts i.e. type A ( blends of 30:70 %); type B (15: 85%) and
type C (0:100%) camels to cow’s milk was the same in the fresh product
1.05% However, it progressively increased with the increase of storage
period at a 6° C , where it reached after 10 days of storage 1.1 % in
type A yoghurt; 1.07% % in type B yoghurt and 1.11 % in type C
yoghurt with a concomitant decrease in the pH values. There was also
a progressive decrease in the protein and total solids contents and a
progressive increase in the fat contents of all the types of yoghurts with
the increase in the storage period for all the types of yoghurts. The
sensory evaluation results indicated that the 100% cow’s milk yoghurt
(type C yoghurt) scored the highest overall acceptability and that type
B yoghurt (15: 85% camels / cow’s milk scored the second best overall
acceptability. It is recommended that camel`s milk utilization
enhancement to be explored by its incorporation in yoghurt
manufacture.
Key words: Quality characteristics; yoghurt; camel’s; cow's milk; food
processing.
INTRODUCTION
The Sultanate of Oman is located between latitudes 16’ 40N
and 26’ 200N and longitude 51' E and 50’ 40E. According to the
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
Quality characteristics of yoghurt made from various blends of camel’s and
cow's milk
EUROPEAN ACADEMIC RESEARCH - Vol. V, Issue 10 / January 2018
5430
Ministry of Agriculture, the number of different livestock (in
thousands) in the Sultanate was 326.240 cows, 1685.420 goats,
380.990 sheep and 127.010 camels were in the year 2009. In
respect of local production of poultry meat, table eggs and fresh
milk, it is evident that fresh milk production has rising trend
from 2007 (47.63 thousand tons) to 2009 (49.57 thousand tons)
(MOA, 2009). Milk is defined as the lacteal secretion obtained
by the complete milking of one or more mammalian animals. It
is highly valued because it is an important source of many of
the nutrients essential for the proper development and
maintenance of the human body. Facts show milk as the
healthiest drink (WWW.dairyfarmingtoday.org). Cows are the
main source for the milk supplies; they produce 90% of the
world total supply of milk (AOAD, 1983). Milk and milk
products have been used as important food for man since before
the dawn of civilization. From historical experience, they have
long been regarded as the best cornerstone to build nourishing
diets. Primitive people had little reason to be concerned with
protein foods when they had milk in their diets. They had to be
concerned with preservation of milk in its various forms (Carls,
1978). Camel milk is obtained from camels. This type of milk is
much more common than other types of milk in native camel
habitats, which are usually very hot and dry. Unlike many
other animals, camels can withstand very dry climates with
little water. Some studies suggest that camel milk is also
healthier than the regular cow`s milk common in the west.
Although it is somewhat common in Middle Eastern countries,
this type of milk is rare in countries like the United States
(Wise, 2011). Yoghurt is a cultured dairy product .The process
of making yoghurt involves culturing cream of milk with live
and active bacterial cultures which prepared by adding bacteria
directly to the milk (Enda, 1998). Several factors are crucial for
successful yoghurt making, which include: good sterile
technique, proper sterilization and cooling of the milk ensure
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
Quality characteristics of yoghurt made from various blends of camel’s and
cow's milk
EUROPEAN ACADEMIC RESEARCH - Vol. V, Issue 10 / January 2018
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good results; proper incubation temperature (50ºC) and
protection of the starter from contamination. The objective of
this work was to process of yoghurt by using cow`s, camel`s
milk and mixed milk (cow and camel) for manufacturing
yoghurt and to Assess of the chemical, microbiological and
sensory quality of manufactured yoghurt as well as to study the
effect of refrigerated storage on the shelf life of the
manufactured yoghurt.
MATERIALS AND METHODS
Materials
Fresh camel milk was collected from Suhil farm in the
mountain (Salalah, Sultanate of Oman) and fresh cow milk was
collected from Sahanot farm in Salalah during the last of
November, then the samples were refrigerated to suppress
microbial growth. Chemical and microbiological analysis were
conducted on milk samples (cow milk , camel milk, 30% camel
milk +70% cow milk, 15% camel milk +85%cow milk) and
yoghurt samples one by pure cow`s milk and the other two
samples using different ratios of cow`s milk and camel milk.
The chemical and microbiological analysis for yoghurt samples
were conducted after one day of the manufacture, after five
days and after ten days. The used glassware and other
materials were sterilized by dry and wet sterilization. The hot
sterilization was done by oven at 148˚C for 3 hours, while wet
sterilization was carried out in an autoclave at 121˚C for 15
minutes. Violed red bile agar and plate count agar
microbiological media were obtained from Oxoid Ltd (UK) and
wort agar was obtained from Lab M limited (UK). All used
microbiological media were prepared according to the
manufactures instructions. In addition, other materials were
used in the manufacture of yoghurt such as stabilizer, skimmed
milk powder and culture.
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
Quality characteristics of yoghurt made from various blends of camel’s and
cow's milk
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Methods
Microbiological media
Plate count agar (PCA), violet red bile agar (VRBA) and potato
dextrose agar (PDA) were used as a standard preparation for
media.
Titratable acidity and pH
For acidity, 10 ml of each sample was pipette into a 100 ml
conical flask, one ml phenolphthalein were then added,
titration was carried out using 0.1 N NaOH until a faint pink
color was obtained. pH values were determined by pH meter
after calibrating it by buffer solution at pH 7.0 and temperature
25˚C.
Protein content
Protein content was determined according to Kjeladahel
method described by (AOAC, 1990). Tow grams of each samples
were placed in digestion flask (500 ml), KSO4 was added to it.
Then 25 ml of concentrated sulfuric acid was added and the
content was heated at 35˚C in fume cupboard until a clear
solution was obtained (2-3 hours) and left to cool before those
antidumping granuleswas added. The digested samples were
poured in a volumetric flask (100 ml) and diluted to 100 ml with
distilled water. Five ml were distilled using 10 ml of 40%
NaOH; 25 ml of boric acid with drops of methyl red were placed
in a conical flask. Distillation of the reaction mixture liberated
ammonia and reacted with boric acid, changing the color from
red to light greenish blue. Excess alkali was then titrated using
0.1 N hydrochloric acid, until color changed to light purple. The
titration reading was reported. The protein content was
determined by multiplying the percentage nitrogen by
empirical factor 6.36; as follow:
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
Quality characteristics of yoghurt made from various blends of camel’s and
cow's milk
EUROPEAN ACADEMIC RESEARCH - Vol. V, Issue 10 / January 2018
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N% = Volume of HCl ×N×14×
Protein % = N% ×6.63 N = Normality of HCl
Total soluble solids content
The total soluble solids percentage was determined according to
the modified method of AOAC, (1990). Three grams of each
sample were weight into a dry clean crucible dish, and then
heated on a water bath for 10 – 15 min. The dish was placed in
an oven at 70˚C overnight, and then cooled in desicator and
weight quickly.
Fat content
A rapid volumetric as described by Foley and Murphy, (1974)
was used for determination of fat content of different samples.
Ten ml of concentrated sulfuric acid was poured in
abutyrometer tube. Then 10.94 ml of mixed milk was added
slowly at the sides, followed by 1.0 ml of fat – free amyl alcohol,
which was also added slowly at the sides, the tube was closed
with especial metal and rubber stoppers and the content
thoroughly and immediately centrifuged at 1100 rpm for 10 min
.The tube was then transferred to a water bath at 65˚C for 3
min for complete fat suspension. The percentage of fat was
determined directly from butyrometer neck.
Lactose determination
The procedure of AOAC, (1980) was used for the determination
of lactose. Firstly,pipetted 5 ml from each Fehling A + B in a
conical flask determined the invert sugar and then 10 ml of
distilled water was added, then 3 – 5 drops of methylene blue
was added as an indicator. The lactose standard was titrated
until the final red precipitate occurred. Fehling factor was
calculated from the following equation. Fehlingfactor: the
titration ×the concentration after that the lactose was
determined by prepared 10 ml of yoghurt (steamed or without
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
Quality characteristics of yoghurt made from various blends of camel’s and
cow's milk
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treatment) in 100 ml volumetric flask. Then the volume was
completed to 100 ml by adding distilled water. After that the
mixture was filtered. Finally, the sample was titrated against
felling solution (A + B) as before. Then the concentration of
lactose was calculated from the following equation:
Lactose % =
Microbiological analysis
Total count of bacteria
The total plate count of microbes were enumerated by culturing
them on Plate Count Agar (PCA) which dissolved in distilled
boiling water, then transferred to bottle and sterilized in an
autoclave (121˚C for 15 min). Then the media with culture was
incubated for 24 - 48 hours at 37˚C.
Yeast and molds count
The yeast and mold strains were enumerated by culturing them
onpotatodextrose agar (PDA) medium and incubating for 72
hours at 25˚C. The media was first dissolved in distilled water
by boiling, transferred in 250 ml conical flasks, sterilized in an
autoclave (15 Psi - 121ºC for 15 minute), and then cooled to
room temperature before used.
Coliform bacteria count
One ml of each of the dilution was inoculated aseptically in
triplicates of 9 ml sterilized Mac Conkey broth using the
Durham tubes. The tubes were incubated at 37˚C for 48 hours.
Positive tubes gave gas in the Durham tubes. Then the positive
tube were sub cultured into EC broth medium and then
incubated at 44.5˚ C for 24 hours to determine the faecal
coliform bacteria, the tube showing any amount of gas
production were considered positive. Mac Conkey broth and EC
medium broth were used as a medium.
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
Quality characteristics of yoghurt made from various blends of camel’s and
cow's milk
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Manufacture of yoghurt
First the skimmed milk powder were added to pasteurized
milk, after that pasteurized yoghurt milk at 90˚C for 10
minutes and cooled to 44˚C then culture was added after that it
was packed into consumer packs immediately transferred to the
incubation room, incubated at 44-46˚C for 4 hours the pH was
reached 4.6 then stored in refrigerator. The samples were coded
as C.
The process started with preparation milk (15% camel
milk with 85% cow milk then skimmed milk powder and
stabilizer were added to the milk and pasteurized yoghurt milk
at 90˚C for 10 minutes after that cooled to 44˚C in this
temperature the culture was added then packed and
immediately incubated in the incubation room for 4 hours at 44-
46˚C the pH was reached 4.55 then stored in refrigerator. The
samples were coded as B.
In process of skimmed milk powder and stabilizer were
added to pasteurized milk (30% camel milk with 70% cow milk),
then pasteurized yoghurt milk at 90˚C for 10 minutes and
cooled at 44˚C then culture added and packed into consumer
packs after that immediately incubated in the incubation room
for 4 hours at 44 - 46˚C (pH reached 4.56) then stored in
refrigerator. The samples were coded as A. Also another two
batches of yoghurt were prepared, one batch by 100% camel
milk and the other batch by 50% camel milk + 50% cow milk,
followed the same way the previous manufacturing but the
incubation period was increased to 9 hours, at the end of the
incubation period were obtained the pH 4.47 for yoghurt
prepared 100% camel milk and pH 4.45 for yoghurt prepared by
50% camel milk.
Chemical and microbiological analysis of yoghurt
Chemical analysis including fat, protein, acidity, pH and solids
were conducted on different samples of yoghurt stored at 6˚C
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
Quality characteristics of yoghurt made from various blends of camel’s and
cow's milk
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for different intervals of time (1 day, 5 days and 10 days).
Microbiological analysis (coliform, total count of bacteria, yeast
and mold) were conducted on different samples of yoghurt
stored at 6˚C for different intervals of time (1 day, 5 days, and
10days).
Sensory evaluation of processed yoghurt
All kinds of yoghurt were displayed for sensory evaluation
using 15 panelists at the second day of storage. The panelists
were asked to evaluate samples by appearance, flavor, taste,
texture, overall ranking and using 5 points, top mark for 5 and
less marked for 1. Sensory evaluation has been done in a quiet
and comfortable place. Each panelist was provided with water
for rinsing. All these conditions were equalized for all tests. The
samples were given codes before being tested.
Statistical analysis
All scores of the sensory evaluation were analyzed by the
analysis of variance (ANOVA). To determine whether there
were significant differences between means for each variable,
least significant difference (LSD test) was used.
RESULTS AND DISCUSSIONS
Chemical composition of camel`s and cow`s milk
The chemical composition of cow`s and camel`s milk are
presented in Table1. The average pH at room temperature, of
camel`s milk 6.96, was higher than that of cow`s milk 6.58, and
also was higher than that of the blend containing 30% camel`s
milk and 70% cow`s milk 6.74 and higher than that blend
containing 15% camel`s milk and 85% cow`s milk 6.76. However
cow`s milk pH (6.58) was approximately similar to the values
reported by Paul and Southgate,(1979) and Salih, (2010), who
reported a values of (6.6) and (6.4±0.17), respectively. The
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
Quality characteristics of yoghurt made from various blends of camel’s and
cow's milk
EUROPEAN ACADEMIC RESEARCH - Vol. V, Issue 10 / January 2018
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camel`s milk pH value (6.96) was higher than that reported by
Farah, (1993) who reported a value of 6.6 in camel`s milk.
The titrable acidity of camel`s milk (0.15%) was higher
than that of cow`s milk (0.14%) and lower compared to that of
30% camel`s milk/70% cow`s milk (0.17%) and 15% camel`s
milk/ 85% cow`s milk (0.16%), and it was similar to the value
reported by Elamin and Wilcox ,(1990) who gave a value of
(0.15%) in camel`s milk, cow`s milk acidity lower than that
reported by Paul and Southgate, (1979) which was (0.2%) in
cow`s milk, also lower than that reported by Salih, (2010) who
found a value of (0.16±0.01 %) in cow`s milk. Table 1,
alsoshowed that the camel`s milk had a lower content of protein
(2.87%) than cow`s milk (2.91%) , 30% camel`s milk 70% cow`s
milk (2.91%) and 15% camel`s milk /85% cow`s milk (2.89%),
the protein content of camel`s milk was higher than that
reported by Elamin and Wilcox ,(1990) who reported a value of
(2.8%) in camel`s milk, and cow`s milk protein was lower than
those reported by Paul and Southgate ,(1979) and Salih, (2010)
for cow`s milk who found a value of (3.3% ) and (3.47±0.18 %),
respectively. The fresh camel`s milk had a higher content of fat
(3.76%) compared to that of cow`s milk (3.50%), and also higher
than that reported by Elamin and Wilcox, (1990) who gave a
value 3.2% in camel`s milk and had lower content compared
with that of 30% camel`s milk/ 70% cow`s milk (3.87%) and 15%
camel`s milk / 85% cow`s milk (3.87%). Cow`s milk fat was
lower than that reported by Salih, (2010) who found a value of
(4.20±0.21 %) in cow`s milk.
Table 1. Some Quality Characteristics of Camel`s, Cow`s and blends of
Camel`s and Cow`s Milk (%): 15% Camel milk 85%
Cow milk
30% Camel milk 70%
Cow milk
Cow milk Camel milk Milk Sample
Component
6.76±0.11 6.74±0.05 6.58±0.07 6.96±0.11 pH
0.162±0.19 0.171±0.11 0.144±0.02 0.153±0.13 Acidity
2.89±0.10 2.91±0.12 2.91±0.11 2.87±0.09 Protein
3.87±0.07 3.87±0.14 3.50±0.15 3.76±0.12 Fat
12.45±0.11 12.48±0.09 12.1±0.12 12.25±0.15 Totalsolids
4.34±0.08 4.37±0.12 4.36±0.13 4.30±0.08 Lactose
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The total solids content of cow`s milk (12.1%) was lower
compared with that of camel`s milk (12.25%), 30% camel`s milk/
70% cow`s milk (12.48%) and 15%camel`s milk /85% cow`s milk
(12.45%) (Table 1) and these values were lower than those
reported by Tekinisk, (1956) and Salih, (2010) for cow`s milk
(12.8%), (13.30±0.20 %), respectively and higher than that
reported by Elamin and Wilcox,(1990) for camel`s milk 11%.
The lactose content of camel`s milk (4.30%) was lower
compared with that of the other types of milk, cow`s milk
(4.36%), 30% camel`s milk/ 70% cow`s milk (4.37%) and 15%
camel`s milk/ 85% cow`s milk (4.34%). (Table 1), and was higher
than that reported by Elamin and Wilcox, (1990) who reported
4.2% of camel`s milk. Cow`s milk had a lower content of lactose
compared with that reported by Salih, (2010) who gave a value
of (4.65±0.28 %) in cow`s milk.
Microbiological composition of milk
The microbiological characteristics of fresh camel`s milk, cow`s
milk, 30% camel milk/70% cow milk and 15% camel milk /85%
cow milk are presented in Table 2. The coliform count in sample
3 (30% camel`s milk/ 70% cow`s milk) and sample 4 (15%
camel`s milk/ 85% cow`s milk) was (0.8×10¹) and (0.9×10¹)
cfu/ml, respectively, and the microbiological analyses revealed
absences of coliform in camel`s and cow`s milk. The total count
of bacteria of camel`s milk (0.1×10² cfu/ml) was less than that of
cow`s milk (0.3×10² cfu/ml), 30% camel`s milk/ 70% cow`s milk
(0.8×10² cfu/ml) and 15% camel`s milk/ 85% cow`s milk (0.5×10²
cfu/ml). Table 2.illustrated also that the yeast and molds count
in camel`s milk cow`s milk, sample 3 (30% camel`s milk /70%
cow`s milk) and sample 4 (15% camel`s milk / 85% cow`s milk)
were (0.3×10¹), (0.2×10¹), (0.4×10¹) and (0.1×10²) cfu/ml,
respectively (Table 2).
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
Quality characteristics of yoghurt made from various blends of camel’s and
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Table 2. Microbiological analysis of milk (cfu/ml)
15% Camel`s milk
85% Cow`s milk
30% Camel`s milk
70% Cow`s milk
Cow`s
milk
Camel's
milk
Parameter
0.9×10¹ 0.8×10¹ Nil Nil Coliform
0.5×10² 0.8×10² 0.3×10² 0.1×10² Total count of
bacteria
0.1×10² 0.4×10¹ 0.2×10¹ 0.3×10¹ Yeast and Molds
Chemical Composition of Yoghurt
The chemical composition of yoghurt is presented in Table 3.
The average pH was gradually decreased during fermentation
when yoghurt was processed, this reduction was clear in the
three types of yoghurt A (yoghurt prepared by 30% camel`s
milk/70% cow`s milk), B (yoghurt prepared by 15% camel`s
milk/85% cow`s milk) and C (yoghurt prepared by 100% cow`s
milk). The reduction in pH was greater in yoghurt type A, B, C
after 1 day of storage, the reduction in pH continued until the
fifth day of storage in yoghurt type B and type C. However,
after 10 days of storage the reduction in pH was continued in
yoghurt type A and type B and there was no change in yoghurt
type C. On the other hand, the titrable acidity increased by
fermentation of yoghurt. The increase in acidity in the three
types of yoghurt (A, B, C) were similar (1.05 %) after 1 day of
refrigerated storage (6°C). The increase in acidity was
continued until the fifth day of storage in yoghurt type A
(1.07%), B (1.06%) and C (1.06%). However, after 10 days of
storage the increase in acidity was continued in the three
yoghurt types A (1.10%), B (1.07%) and C (1.11%). Figure 1
describes the relationship between pH and titrable acidity
during fermentation of yoghurt type A and yoghurt type B,
which indicated decrease of pH and increase of acidity. On the
other hand, Fig 1. describe the relationship between pH and
titrable acidity during fermentation of yoghurt prepared by
100% cow`s milk (type C), this Fig revealed decrease in pH until
the fifth day of storage, after that the pH was constant, the Fig
also indicated the increase of acidity especially after 10 days of
storage.
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
Quality characteristics of yoghurt made from various blends of camel’s and
cow's milk
EUROPEAN ACADEMIC RESEARCH - Vol. V, Issue 10 / January 2018
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Table 3. Some quality characteristics of various types of yoghurts (%).
Storage Period (Days)
Parameter Ten Five One
C B A C B A C B A
4.3 4.3 4.3 4.3 4.4 4.4 4.4 4.5 4.4 pH
1.11 1.07 1.10 1.06 1.06 1.07 1.05 1.05 1.05 Acidity
15.39 15.56 15.44 15.55 15.67 15.74 15.64 15.72 15.83 Total Soluble Solids
(T.S.S)
4.47 4.47 4.53 4.47 4.59 4.59 4.66 4.79 4.66 Protein
3.48 3.58 3.62 3.41 3.34 3.43 3.36 3.24 3.30 Fat
A: Yoghurt prepared by 30% camel milk / 70% cow milk; B: Yoghurt prepared by 15%
camel milk / 85% cow milk; C: Yoghurt prepared by 100 % cow milk.
10 Days
Fig. 1 Relationship between pH and titrable acidity during
fermentation of yoghurt
The protein content of yoghurt type B (4.79%) was higher if
compared with yoghurt type A (4.66%) and type C (4.66%),
these values decreased until fifth day of storage (A (4.59%), B
(4.59%), C (4.47%), after 10 days of storage the reduction in
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
Quality characteristics of yoghurt made from various blends of camel’s and
cow's milk
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protein continued in yoghurt type A (4.53%) and type B (4.47%)
and there was no change in yoghurt type C (4.47%).
Table 3. also showed that the fat content of yoghurt type
C (3.36%) was higher than that of yoghurt type A (3.30) and
type B ( 3.24%), fat content were increased in the three types of
yoghurt A (3.43%), B (3.34%) and C ( 3.41%) until 5th day of
storage. However, after 10 days of storage the increased in fat
content was continued in the three yoghurt types A (3.62%) , B
(3.58%) and C (3.48% ) .
Microbiological analysis of yoghurt
Table 4, showed the microbiological characteristics of yoghurt
during storage at 6°C for 1, 5 and 10 days. The coliform
bacteria count was higher in yoghurt prepared from a blend of
15% camel`s milk and 85% cow`s milk designated as yoghurt
type B (4.0×10² c.f.u/g) than that in yoghurt prepared from a
blend of 30% camel`s milk and 70% cow`s milk designated as
yoghurt type A (0.8×10¹c.f.u/g) and yoghurt prepared by 100%
cow`s milk designated as yoghurt type C (0.5×10¹ c.f.u/g ) and
decreased after 5 days of storage in yoghurt type B (2.4×10²
c.f.u/g) and there were no change in yoghurt type
A(0.8×10¹c.f.u/g) and C (0.5×10¹ c.f.u/g ). However, after 10
days no change observed in coliform count in yoghurt type C
(0.5× 10¹ c.f.u/g) but there was decrease in yoghurt type B
(0.7×10¹ c.f.u/g) and increase in yoghurt type A (2.2×10¹ c.f.u/g).
Table 4. Microbiological analysis of various types of yoghurt (cfu/g) Storage Period (Days)
Parameter Ten Five One
C B A C B A C B A
0.5×10¹ 0.7×10¹ 2.2×10¹ 0.5×10¹ 2.4×10² 0.8×10¹ 0.5×10¹ 4.0×10² 0.8×10¹ Coliforms
1.3×10²
6.0×10⁴ 4.6×10² 1.2×10² 1.7×10⁴ 4.0×10² 5.5×10² 1.8×10⁴
1.8×10³
Total count of
bacteria
0.7×10¹ 5.0×10² 1.0×10ᶾ 0.7×10¹ 0.9×10¹ 0.4×10¹ 0.7×10¹ 3.0×10² 0.4×10¹ Yeast and
Molds
A: Yoghurt prepared by 30% camel milk /70% cow Milk; B: Yoghurt prepared
by 15%camel milk / 85% cow milk C: Yoghurt prepared by 100% cow milk
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
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The total count of bacteria of yoghurt type B (1.8×10⁴ cfu/g) was
more to that of yoghurt type A (1.8×10³ cfu/g) and yoghurt type
C (5.5×10² cfu/g) after 1 day of storage , and after 5 days of
storage the total count of bacteria was decreased in yoghurt
type A (4.0×10² cfu/g), yoghurt type B (1.7×104 cfu/g) and
yoghurt type C (1.2×10² cfu/g), after 10 days of storage the total
count of bacteria were increased in the three types of yoghurt ,
type A (4.6×10²cfu/g), type B (6.0×10⁴cfu/g) and type C (1.3×10²
c.f.u/g) .
The yeast and molds count were higher in yoghurt type
B (3.0×10² cfu/g) compared with yoghurt type A (0.4×10¹ cfu/g)
and type C (0.7×10¹ cfu /g), after 5 days of storage yeast and
molds count were decreased in yoghurt type B (0.9× 10¹ cfu/g)
and there were no change in yoghurt A (0.4×10¹cfu/g) and type
C (0.7×10¹) , after 10 days the number of yeast and molds were
increased in yoghurt type A (1.0×10² cfu/g) and type B (5.0×10²
cfu/g) and there was no change in yoghurt type C (0.7× 10¹
cfu/g) .
Sensory evaluation
Sensory evaluation was conducted for the three types of
yoghurt A (yoghurt prepared by 30% camel`s milk / 70% cow`s
milk), B (yoghurt prepared by 15% camel`s milk/ 85% cow`s
milk) and C (yoghurt prepared by 100 cow`s milk) by 15
panelists has included Rating on appearance, flavor, taste,
texture, and overall ranking and got the following results: The
appearance of cow`s milk yoghurt (C) had the highest scores
compared to A and B , with no significant difference between
sample A and B and there is no significant difference between
sample B and C but there is significant difference between
sample A and C. (Table 5). Also the flavor of cow`s milk yoghurt
(C) had the highest scores compared to other samples A and B,
with significant difference between sample A, B and C. For
taste and texture there was no significant difference between
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
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EUROPEAN ACADEMIC RESEARCH - Vol. V, Issue 10 / January 2018
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sample B and C but there was significant difference between
sample A and other samples and sample C had the highest
scores compared to A and C. However, the panelists showed
that the most acceptable yoghurt samples were the yoghurt
made from 100% cow`s milk. Statistically, significant variations
(P ≤ 0.05) were observed in overall acceptability scores between
yoghurt samples.
Table 5. Mean score for sensory evaluation of the three types of
yoghurt.
Quality attribute Samples
Overall acceptability Texture Taste Flavor Appearance
2.07 1.93 1.87 2.07 2.20 A
3.0 3.07 3.13 3.07 3.07 B
4.20 3.80 3.87 4.07 4.0 C
Means are based on a point scale (1 is poor, 2 is unacceptable, 3 is acceptable,4 is good
and 5 is excellent); A = Yoghurt prepared by 30% camel`s milk/ 70% cow`s milk; B =
Yoghurt prepared by 15% camel`s milk/ 85% cow`s milk;C = Yoghurt prepared by 100%
cow`s milk.
CONCLUSION
In the present study, three types of yoghurt were prepared from
camel`s and cow`s milk using different ratios, the first type
prepared by 30% camel`s milk / 70% cow`s milk, second type
prepared by 15% camel`s milk / 85% cow`s milk and third type
100% cow`s milk. Before preparation of yoghurt, the milk
samples were subjected to chemical and microbiological
analysis. Most of the chemical compounds of milk fairly close
with and there are some differences of increase or decrease,
microbiological analysis revealed some of pathogenic bacteria
like total bacteria count and coliform bacteria, also revealed
very few numbers of yeast and molds. Chemical analysis of the
types of yoghurt gave comparable results either for microbial
analysis showed the presence of small numbers of coliform,
total bacteria count, yeast and molds. The manufactured
yoghurt samples showed high nutritive value, especially
Zakaria A. Salih, Azhari Siddeeg, Sahar G.A. Hamid, AL-Farga Ammar, Ali O. Ali-
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cow's milk
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yoghurt that containsa greater proportion of camel milk, where
that camel milk given him greater nutritional value. That
opens the door widely to for using camel`s milk in preparation
of yoghurt in dairy plants in Oman, since camels are important
for milk production especially in Dhofar state. It is known that
most of people avoid consumption of camel`s milk and camel`s
milk products due to its characteristics flavor, using of cow`s
milk with camel`s milk in prepare yoghurt improved the flavor
and texture of yoghurt. Generally, the manufactured yoghurt
samples that contain camel`s milk got to accept less by
panelists compared with cow`s milk yoghurt and it is due to
strength cow`s milk yoghurt best and perhaps that people not
familiar with camel milk products and flavor. There are a
recommendations such as: Addition of flavoring compounds in
the manufacture of camel`s milk products, due to the
unacceptable flavor of camel`s milk, addition of compounds to
improve the texture of yoghurt prepared by camel`s milk to
increase acceptance, more research is recommended on the use
of camel`s milk in manufacture of yoghurt as well as encourage
dairy industries to utilize camel`s milk in production of milk
products.
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cow's milk
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